A reciprocating wind machine usually has a gearbox provided with a suitable motion-translating mechanism for converting the rotary motion of a rotor or sail to the reciprocating motion of a suspended vertical shaft. A rigid frame supports the gearbox and rotor. The vertical reciprocating shaft transmits power from the gearbox to the driven device. The reciprocating wind machine may be used, for example, as a power source for a reciprocating pump.
The load required to operate a reciprocating pump is not uniform throughout the work cycle. The work cycle of a simple vertical reciprocating pump has two phases. In the first or working phase, power is required to lift the pump piston and the water to be delivered by the pump. In the second or return phase of the work cycle, less power is required because no pumping is being done and, also, because the weight of the piston contributes to the force required (if any) to restore the piston to the beginning of the cycle.
If a reciprocating pump imposes an instantaneous load which exceeds the capacity of the wind machine, the system will stall. A wind machine cannot utilize wind whose velocity is slower than the stall speed. The velocity of wind necessary to restart the wind machine is usually somewhat higher than the stall speed. This is because of the compound effects of static friction in the various components of the system.
Conventional wind driven reciprocating pumps are limited by their stall speeds. It is not uncommon for such a device to remain inactive for 30% of the time it is in service due to stalling. Various attempts have been made to lower the stall speed and restart speed, and thereby increase the usefulness of wind driven reciprocating pumps. The primary characteristic of these devices has been the process of redistributing peak loads encountered during one phase of the work cycle to less loaded portions of the work cycle. This usually entails generating potential energy during the return phase of the work cycle where the capacity of the wind machine is not usually utilized and releasing it during the working phase of the cycle where demand is at its highest.
Known in the prior art are systems of weights and pulleys designed to this effect. These have been unsatisfactory in practice and have fallen into disuse.
U.S. Pat. No. 3,782,222, issued Jan. 1, 1974, also deals with this problem. This patent illustrates the use of telescopic arms pivotally attached to the vertical reciprocating shaft. The arms are pivotally secured to rotatable discs carried by the windmill tower. A system of cables and counterweights cooperates with the adjustable telescopic arms to counterbalance the weight of the vertical shaft and pump cylinder. This system is limited by the difficulty of adjusting the two arms accurately and equally in the field and by the mechanical complexity of the assembly of parts, which is in itself a source of costly maintenance and down-time.
U.S. Pat. No. 4,211,126 describes a system for pushing and lifting loads having improved counterbalancing. This system replaces the telescopic arms and cables with two rigid arms carried pivotally by the windmill frame and pivotally attached to the reciprocating shaft.
The rigid arms carry adjustable weights. By moving the weights in the rigid arms, one is able to counterbalance, to some extent, the weight of the vertical shaft and pump piston. Like the '222 patent, this arrangement of pivoting parts is overly complex and carries four stressed pivot joints and two different counterweight adjustments.
Both of the prior art patents are also limited by their structure to delivering reciprocating motion. This form of driving force is suitable for some commonly used driven machines such as reciprocating water pumps and air compressors, but cannot be used on rotating machines such as alternators, generators, or rotary pumps without extensive modification.